There is much interest in miniaturizing devices using cold atoms for applications in precision timekeeping (e.g., atomic clocks), navigation (e.g., inertial sensors), and magnetic sensing. The cold atoms for these devices are used in a vaporized form, and may need to be replenished over time. Replenishing the atoms can be accomplished with a solid source material, which is referred to herein as an evaporable metal material, since the cold atoms comprise metal atoms, often an alkali. A component that includes such an evaporable metal material configured to release metal atoms is referred to herein as an alkali dispenser. An alkali dispenser can be configured to heat the evaporable metal material in order to release the metal atoms therefrom to create the metal atom vapor. Depending on the application, these vaporized atoms can then be cooled and trapped using light and magnetic fields.
There are two types of alkali sources in conventional atomic sensors: active and passive. A conventional passive source can be made small (˜mm size) and are fabricated individually. That is, such passive sources are not compatible with batch fabrication processes and can have a lot of variability from sample to sample. It can be difficult to precisely regulate the atomic vapor pressure over temperature when using such sources as most atomic vapor pressures have very large temperature dependency. Often a second agent is needed to either passively or actively try to control the alkali density from the passive source. Unless made reversible, this is a lifetime limiter.
A conventional active source is typically an alkali dispenser or getter. An active source also can be small (˜mm, pill size), but the required mounting and through-vacuum feeds make the assembly quite large. Such active sources also require large current to activate. The mounting size typically increases the distance from the source to the sensor head (where the sensing takes place), increasing the sensor size and decreasing the efficiency and lifetime of the source.